Solar cells made with organic dyes – cheaper, cleaner

A dye absorbing blue light from a laser pointerCourtesy OMSIDye-sensitized solar cell ready to be testedCourtesy OMSIDid you know that you can make small solar cells out of things like berries, tea, and doughnuts – yum! Berries and teas have dyes (organic molecules that absorb light) that give them color. Instead of using berries, there are researchers synthesizing dyes to use in solar cells. These solar cells are called dye-sensitized solar cells - DSSC for short. DSSCs convert sunlight energy into electrical energy. They work like this. Love that Scottish accent!

Most commercial solar panels are made with silicon because silicon absorbs much of the light spectrum in sunlight. Silicon solar cells absorb a wider range of the light spectrum than DSSCs currently do. The best silicon solar cells are about 20% efficient. The best DSSCs are about 11% efficient. Why use dyes instead of silicon to make solar cells? Dyes are much cheaper and less resource intensive to make. Most silicon cells are made from purified single-crystal silicon. About 40% of the crystal is lost as it is sliced into thin wafers.

I recently met scientists at Portland State University (PSU) in Portland, Oregon who are working on making dye-sensitized solar cells more efficient. Alex Rudine has been manipulating porphyrin dyes to get them to absorb more of the light spectrum. The advantage of using porphyrins is that they absorb light well and their structure is versatile and relatively easy to manipulate.

In a DSSC, as sunlight hits the dye, an electron is excited and moves to an electron acceptor. An electron flows from the electron donor to fill the hole, creating an electrical current. One of the challenges of DSSCs is that a wet solution of iodide is the typical medium for the electron donor. There are labs working on synthesizing a solid state medium. Carl Wamser’s lab at PSU in Portland, Oregon is one of those. They have synthesized a porphyrin with a nanofiber structure with a very high surface area. A high surface area means there are more places where the energy conversion can happen.

One of the things limiting more wide-spread use of solar energy is the higher set-up costs of solar panels compared to fossils fuels. If researchers can develop a commercially successful DSSC, it would be a cheaper, more sustainable source of solar energy. Unlike burning fossil fuels which releases heat-trapping gases, solar is a clean energy source that doesn’t contribute to global warming. Enough sunlight falls on the Earth in one hour that if we could collect it, we could power for one year all the machines on Earth. That’s an amazing amount of potential clean energy we could tap into.

Researchers at PSU also have a pretty cool experiment running that combines silicon photovoltaic panels with green roofs. Click here to find out more.

Your Comments, Thoughts, Questions, Ideas

CameronRobertson says:

This is something very new to me as I have always thought solar cells can only be built by men and by using metals and such. However, this article has opened up my eyes about the fact that I can make my own solar cells by using only things from my kitchen. I know that plants/fruits absorb sunlight for photosynthesis, but who would have thought that they could be strong enough to hold up an entire storage for sunlight along with them. That is why it is a good practice to read and expand our general knowledge capacity and learn new things everyday.

I'm glad you learned something new from this. Plants are indeed amazing, and we can always learn from the way nature tackles important problems. In this case, we use molecules that are similar to chlorophyll (porphyrins) and strategies that are similar to photosynthesis to come up with our dye-sensitized solar cells. It's an exciting and important field to be in, and I hope you consider it in your future!

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